Voltage detector for sensing and digitally encoding states of potential

ABSTRACT

In a detector for sensing four different states of potential applied to its input and for digitally encoding them at two detector outputs, there are provided two semiconductor components, each connected to the detector input and to one detector output; each semiconductor component is associated with a voltage divider, a reference source, a comparison source and a digital source. On either detector output there may appear either a logic 1 or a logic 0, allowing four possible digital signal pair combinations at the detector output, whereby each digital signal pair characterizes one state of potential applied to the detector input.

United States Patent 1 Harms 3,73LHS May t, 1973 VOLTAGE DETECTOR FORSENSING AND DIGITALLY ENCODING STATES OF POTENTIAL Inventor:Wolf-Henning, Harms, Berlin, Germany [73] Assignee: krone GmbHBerlin-Zehlendosb,

Germany Filed: May 12, 1971 Appl. No.: 142,534

[30] Foreign Application Priority Data May 12, 1970 Gennany ..P 20 23164.5

References Cited A UNITED STATES PATENTS 2,975,305 3/1961 Pinet..307/255 OUTPUT Primary Examiner-John W. Huckert Assistant Examiner-B.P. Davis Attorney-Edwin E. Greigg ABSTRACT In a detector for sensingfour different states of potential applied to its input and fordigitally encoding them at two detector outputs, there are provided twosemiconductor components, each connected to the detector input and toone detector output; each semiconductor component is associated with avoltage divider, a reference source, a comparison source and a digitalsource. On either detector output there may appear either a logic 1 or alogic 0, allowing four possible digital signal pair combinations at thedetector output, whereby each digital signal pair characterizes onestate of potential applied to the detector input.

7 Claims, 3 Drawing Figures OUTPUT Patented May 1,' 1973 3,731,118

2 Sheets-Sheet 1 Fig. j (PRIQR ART) -55 v A'LZI- .41 1, OUTPUT 1 F f is;5

. i'* ouTPuT OUTPUT- Patented May 1, 1973 3,731,118

2 Sheets-Sheet 2 Fig. 2'

ll H u u VOLTAGE VOLTAGE /DIV|DER /DIVIDER 2 0uTPuT "OUTPUTSEMICONDUCTOR COMPONENT V %8S$ la lb 110 5g 5b 4b REFERENCE COMPAR-COMPAR- REFERENCE SOURCE ISON ISON SOURCE SOURCE SOURCE INPUT VOLTAGEDETECTOR FOR SENSING AND DIGITALLY ENCODING STATES OF POTENTIAL OBJECTAND SUMMARY OF THE INVENTION It is an objectof the invention to providean improved detector of the aforenoted type from which the disadvantagesinherent in the use of relays is eliminated.

Briefly stated, according to the invention, the detector comprisessemiconductor components, each connected by means of an associatedtwo-part voltage divider to an associated digital source delivering a lor potential, and to a reference source delivering a potential whichcorresponds to one of the states of potential and which is smallerthan'the 0 potential or, respectively, greater than the 1 potential. Theratio of resistances in each voltage divider is so designed that in casethe associated semiconductor component is in a conductive state, thecenter tap of the voltage divider has an 0 or, respectively, an 1potential. The center taps of ADVANTAGES AND EXEMPLARY USES OF THEINVENTION The use of semiconductor components in the detector has theadvantage that the detection may be effected with components of highohmic resistance, so that the detector will not interfere with the stateof potential of the line connected to the detector input. In addition,the potentials to be detected may be arbitrarily large, while thenecessary sensing periods will be extremely small. Further,semiconductor components, besides a very high switching speed, consumeonly an extremely small current. Due to the small current consumption,the power necessary to operate the detector is also very small. Inaddition, no inductivities' are present, so that thenegative effect theywould have on the circuit connected to the detector input is eliminated.

The aforenoted semiconductor components may be transistors, thyristors(for regulating circuits), lighttriggered phototransistors (forelectron-optical circuits), or integrated semiconductor components forprecision detection.

The detector according to the invention may find advantageousapplication in thescanning of telephone lines regarding their state ofpotential. It is noted that according to the standardsof the GermanFederal Post .sequently transmitted through a time multiplextransmission line.

For such an application, the structure of the detector according to theinvention may be simplified by providing that the semiconductorcomponents are transistors and that the reference source of onetransistor is at the same time the comparison source for bothtransistors.

It is further expedient to provide that the potential of the referencesources corresponds to the lowest state of potential whereby an exactthreshold is reached only for this condition and that the digitalsources transmit a 1 potential, whereby a direct control of the TTLcomponents from this digital source may be directly achieved withouttransducer circuits.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a circuit diagram of adetector according to the prior art;

FIG. 2 is a block diagram illustrating the principles of a detectoraccording to the invention and FIG. 3 is a circuit diagram of apreferred embodiment of the invention.

BACKGROUND OF THE INVENTION This invention relates to a detector for thedigital encoding, at two output terminals, of up to four differentstates of potential applied to its input terminal. To each outputterminal there is applied, over separate switches associated with eachoutput terminal, a logic 1 or a logic 0, dependent upon a comparison ofthe state of input potential with the potential of comparison sourcescorresponding to these four states of potential.

Detectors of the aforenoted type are adapted to supervise telephone andteletypewriter lines and regulating circuits used in regulatingtechniques.

A detector of the aforenoted known type is illustrated in FIG. 1 and mayfind application in supervising the state of potential of telephonelines wherein three different states of potential (negative potential,ground potential and floating ground or floating potential) may appear.Such a detector is also described in R. Fuhrer: LandesfernwahlGe'ratetechnik, page 208.

As shown in FIG. 1, with an input terminal E there are connected thecoils of two electromagnetic relays E and F; To the relay F there isapplied, through a switch SF, a negative potential of a comparisonsource (not shown), while the relay E is connected, through a switch SE,to the ground potential which serves here as positive potential. Therelays E and F comprise respective relay contacts e and f which aredirectly connected to respective output terminals 1 and 2. Each relaycontact e and f may be switched between two poles, of which one isconnected with a potential source delivering a logic 1 and the other iscoupled with a potential source delivering a logic 0.

It is apparent from FIG. 1 that the two switches SE and SF must not besimultaneously in a closed position because in such a case both relayswould be energized continuously by virtue of a current flowing from theground to the reference source of negative potential. For this reason,the switches SE and SF are controlled by beat pulses which are out ofphase and which are delivered by conventional beat generators, notshown.

In order to obtain signals simultaneously at the outputs l and 2 despitean alternating closing of the switches SE, SF (which results in analternating detection of the input E through the two relays E and F) therelays E, F are delayed response relays, that is, they remain in anattracted (energized) position for a certain duration, for example, forseveral pulse periods, even after opening of the respective switches SEor SF (i.e. even after the interruption of the current flowing throughthe respective relay).

The data in the table given below for the detector according to FIG. 1will become readily apparent if it is considered that during currentflow through the relays E or F, the respective relay contacts e and fare in a position opposite to that shown in FIG. 1.

State of Input Potential Output 1 Output 2 Negative Potential' 1Positive Potential (Ground Potential) 0 l Floating Potential O O Theaforeoutlined detector has several disadvantages. Its delay of responseis obviously quite significant because of the inertiaof the mechanicalcontacts. Further, the relay resistance has to be relatively low becauseof technological reasons and because of the requirement to maintain theinductivity at a low value. Consequently, a detector of this typeconsumes substantial power and for'this reason, as well as by virtue ofthe inductivity of the relay coils, the supervised line is interferedwith in a significant degree.

OUTLINE, CHARACTERISTICS AND ADVANTAGES OF A PREFERRED EMBODIMENT OF THEINVENTION According to a preferred embodiment of the invention describedin more detail later with reference to FIG. 3 the first transistor is ann-p-n transistor and the second transistor is a p-n-p transistor andfurther, the input terminal is connected to the reference sourceassociated with the first transistor through a resistance of high ohmicvalue. The input side terminal of said resistance is connected to thebase of the first transistor, while the other terminal of saidresistance is connected to the emitter of the first transistor. In thismanner, the

' detector at the input side has a high ohmic value with respect to thelowest state of potential, whereby interferences with the lines to bedetected may be prevented. Simultaneously, by virtue of the largevoltage drop between the emitter and the base of the first transistor, acomplete conductivity thereof is achieved.

According to the preferred embodiment, the input is connected with thedigital source of the second transistor through. a Zener diode and athird voltage divider. That terminal of the third voltage divider whichis remote from the Z-diode is connected to the emitter of the secondtransistor and further, the center tap of the third voltage divider isconnected with the base of the second transistor. The ratio of the thirdvoltage divider is so selected that during the conductive state of theZ-diode, the base of the second transistor is negative with respect tothe emitter. In this manner the switching threshold for the higheststate of potential is determined alone by the Z-diode and for the othertwo states of potential there is sufficiently negative potentialavailable at the center tap of the third voltage divider to ensure thatthe second transistor is rendered securely conductive.

It is further advantageous if the digital source of the secondtransistor transmits a 1 potential and that the Z- diode has a gatingvoltage which corresponds to the desired switching threshold for thehighest state of potential and which has a magnitude that is at leastidentical to the 1 potential. In this manner there is ensured an exactswitching threshold even for the highest state of potential. This,together with a high ohmic resistance at the input, contributes to ahigh input resistance of the detector.

The gating voltage of the Z-diode should have a magnitude equal at leastto the 1 potential because of the following considerations:

The second transistor can close and thus deliver a l potential at thesecond output only when there is applied a potential to its base that isidentical to, or more positive than the potential applied to itsemitter. Thus, the latter is at a 1 potential applied, for example,through a resistance of the second voltage divider. Since a morepositive potential cannot appear if the second output is closed with avery large ohmic resistance, it has to be ensured that at least thelastnamed 1 potential also appears at the base. Thus, in such a casethere must be no current flow through the third voltage divider. Such aresult is, however, achieved only if the Z-diode is in a blocking stateup to the 1 potential. This is the condition for an 1 potential toappear at the base of the second transistor (and thus allowing it toassume its blocking state) through one half of the third voltage dividerduring application of the highest state of potential to the detectorinput.

It is noted that the potential at the emitter of the second transistorcould be lowered by a voltage drop of A U,; across the already mentionedresistance of the second voltage divider by providing a coupling memberof low ohmic resistance at the second output. In such a case the gatingvoltage of the Z-diode may be by A U lower than the 1 potential while ablocking of the second transistor would be still ensured. It is,however, a desideratum not to use any low-ohmic coupling members andtherefore the blocking voltage should be fixed at the 1 potential. Insuch a case a secure blocking is always ensured and the couplingresistance may be of any desired value.

According to a further development of the invention, the first voltagedivider is disposed between the collector of the first transistor andits associated digital source and further, one half of the secondvoltagedivider is disposed between the digital source of the secondtransistor and the emitter thereof and the other half of the secondvoltage divider is disposed between the collector of the secondtransistor and the reference source associated therewith. In thismanner, in case the highest state of potential prevails at the input, atthe emitter of the second transistor there is securely obtained apotential which is somewhat more negative than that prevailing at thebase, since the output current flows through the resistance of thesecond voltage divider disposed between the second digital source andthe emitter and thus a voltage drop occurs. Consequently, the secondtransistor is securely blocked although no current may flow through thethird voltage divider because of the Z-diode. As far as the firsttransistor is concerned, there is no need of a division of the firstvoltage divider, since a current flow is always possible from the inputto the emitter of the first transistor and thus the emitter-base voltageconditions permit the first transistor to assume without difficultyeither a blocking or a conductive state.

The aforeoutlined preferred embodiment may be simplified by omitting thesecond half of the second voltage divider, so that the emitter of thesecond transistor is directly connected to the reference source having apotential. The last-named reference source is constituted by a readilyavailable 0 potential source.

It is further expedient to connect the center tap of the first and thesecond voltage dividers to an O potential source through separatediodes. If, in such a structure, the highest .state of potential equalsthe ground potential, the diodes prevent an inadvertent application of anegative potential to the two output terminals. Such an occurrence (i.e.the application of a negative potential) cannot be tolerated in case atransistortransistor-logic (TTL) circuit is coupled to both out puts.According to data sheets of TTL components (see, for example, TexasInstrument Series SN 74), the latter must be controlled exclusively withpositive voltages, since negative voltages would cause their immediatedestruction.

In viewof the foregoing, the use of a detector built in theaforeoutlinecl manner permits a direct control of integrated TTLcircuits.

DESCRIPTION OF AN EMBODIMENT ILLUSTRATING THE PRINCIPLES OF THEINVENTION .Turning now to FIG. 2, there is shown a block diagram of adetector for digital encoding according to the invention.

Two semiconductor components 1a and 1b are each connected to a detectorinput to which the states of potential to be sensed are applied. Eachsemiconductor switch 1a, lb is further connected through a respectivetwo-part voltage divider 2a and 2b to respective digital sources 3a and3b, which deliver a logic I and a logic 0 potential, respectively. Thecenter taps of each twopart voltage divider 2a and 2b constitute arespective output 1 and 2 of the detector.

Each semiconductor component 1a and 1b is further connected to arespective reference source 4a and 4b having a fixed potential and-to arespective comparison source 5a and b, also having a fixed potential.

' The switching state of the semiconductor switches la and 1b thusdepends, upon the potential difference between the input on the'onehand, and the associated respective comparison sources 5a and 5b, on theother hand.

It may be. directly observed from FIG. 2 that in case of a blockedsemiconductor switch 1a or 1b, the logic potential of the associateddigital source3a or 3b is applied through the voltage divider 2a or 2bto the output 1 or 2.

In case the semiconductor components 14 and lb are in a conductivestate, the potential difference between the reference source 4a or 4band the digital source 3a or 3b is applied to the associated output 1 or2 through the associated voltage divider 2a or 2b. Consequently, theratio of resistances in thevoltage dividers 2a and 2b and the potentialof the reference sources 4a and 4b have to be selected in such a mannerthat even in a conductive state of the semiconductor components thereprevails a logic potential which is opposed to the logic potential ofthe associated digital sources or 3b, respectively.

If thus, for example, the digital source 30 delivers a logic 1 potentialand, in a blocking state of the semiconductor component 1a thispotential is applied through the center tap of the voltage divider 2a tothe output 1, then during the conductive state of the semiconductorswitch la, at the output 1 there must appear a logic potential 0 byvirtue of the cooperation of the digital source 3a, the reference source4a, and the voltage divider 2a (the resistance of the semiconductorcomponent la is neglected in the conductive state). Thus, in this case,the potential of the reference source 4a has to be below the logicpotential 0. It is noted that if the digital source 3a delivered an 0potential then, accordingly, the reference source 4a should be at apotential which is greater than the 1 potential.

It is further readily apparent from FIG. 2 that because of the twooutputs l and 2 which each may receive two different logic potentials,there are possible a total of four different potential combinations atthe outputs 1 and 2, so that four different states of potential may besensed at the input of the detector according to the invention.

It will be apparent that if further semiconductor components areconnected to the detector input together with associated comparisonsources, reference sources, voltage dividers, digital sources andoutputs, it is possible to increase the number of potential states thatmay be sensed at the detector input. Based on simple mathematicalconsiderations, the number of potential states detectable at the inputis by 2 higher than the number of the detector outputs.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the embodimentdepicted in FIG. 3 and already outlined earlier in the specification, itis assumed that at the input E of the detector there may appear threedifferent states of potential, namely, a negative potential, a groundpotential, and a floating ground or floating potential. v

I The detector comprises an n-p-n transistor Tr, and a p-n-p transistorTr both functioning as switching components. With the transistor Tr,there is associated a first voltage divider formed of two resistancesR,,, R,, and connected to the collector of the resistor Tr, and a firstdigital source P, having a 1 potential of approximately 5 Volts. Thecenter tap of the voltage divider R,,, R, is connected to an output 1.

The emitter of the transistor Tr, is connected with a reference sourceM, having a negative potential. In this embodiment the reference sourceM, also serves as a comparison source for comparing the state ofpotential momentarily prevailing at the input E in order to control thetransistors Tr, and Tr,.

Similarly, with the second transistor Tr there is associated a secondvoltage divider formed of resistances R and R The resistance R isconnected to the collector of the transistor Tr, and a reference sourceM having a negative potential, while the resistance R,, is connected tothe emitter of the transistor Tr, and a second digital source P having a1 potential. The center tap of the second voltage divider which, in caseof a negligible impedance of the emitter-collector leg of the transistorTr, in a conductive state coincides with the emitter thereof, isconnected to an output 2 of the detector.

Normally, P, and P are connected with one another and a common digitalsource of V. A separation of P, and P has significance only in a casewhen the output 1 is in a digital circuit which requires input voltagesother than that applied to the output 2. Thus, for example, there areswitching circuits of the HLL family (High Level Logic) which require Vfor the 1 potential.

The ratio of resistances in the first and second voltage dividers R,,,R, and R R respectively, are selected in such a manner that in theconductive state of the associated transistor Tr, and Tr respectivelythere appears at the center tap a logic 0 potential which in thisinstance is equal to the ground potential. In order to compensate forpossible small negative deviations from the exact 0 potential and thusprotect a coupled TTL circuit from a resulting destruction, there areprovided diodes D, and D through which the respective outputs l, 2 aregrounded.

The input E is, on the one hand, connected through a resistance R to theemitter of the transistor Tr, and, on the other hand, through aZener-diode D and a third voltage divider R R to the second digitalsource P and to the resistance R of the second voltage divider.Resistances R* and R** are the base resistances of the two transistorsTr, and Tr respectively.

The ratio of resistances in the third voltage divider R R is selected insuch a manner that in the conductive state of the Z-diode D thereappears at the base of the second transistor Tr a voltage which isnegative with respect to its emitter, so that the transistor Tr is in aconductive state.

OPERATION OF THE PREFERRED EMBODIMENT In the description that followsthere is set forth the operation of the detector according to FIG. 3 forthe three states of potential at the input E, namely negative potential,ground potential, and floating ground and floating potential.

1. Negative potential applied to input E.

Across the resistance R there is no voltage drop, so that the transistorTr, is blocked and at the output 1 there prevails a 1 potential appliedthrough the resistance R At the Z-diode D there is a blocking voltagedrop of, for example, I5 VI The remaining potential difference betweenthe negative potential at the input and the 1 potential at the digitalsource P is divided between the resistances R and R of the third voltagedivider in such a manner that at the base of the transistor Tr thereprevails a voltage which is negative with respect to its emitter, sothat the transistor Tr is placed in a conductive state. Then, at thecenter tap of the second voltage divider there prevails, by definition,approximately zero Volts or ground potential, that is, an 0 potential,which is forwarded to the output 2. The exact setting of the 0 potentialis effected by the diode D which is weakly conductive for negativevoltages. In this manner, a component particularly a TTL circuitconnected to the output 2 is protected from negative potentials.

2. Ground potential applied to the input E.

In this instance, the entire negative potential drops across theresistance R,;. As a result, the transistor Tr, is rendered conductiveand thus applies to the first voltage divider R,,, R a voltage which isbetween the 1 potential and the negative potential. By definition, an 0potential appears at the center tap of the first voltage divider and theoutput 1. A 'I'TL circuit connected to the output 1 is protected fromnegative potentials by the diode D Since at the input E there prevails aground potential, the Z-diode D is fully blocked, so that at the base ofthe transistor Tr as well as on its emitter there appears a positivepotential supplied by the second digital source P while current flowsfrom the digital source P through the resistance R to the output 2 whereit generates a voltage drop. Consequently, the transistor Tr is blocked,so that at output 2 there appears a 1 potential applied across theresistance R 3. Floating ground and floating potential prevailing atinput E.

In this case, a current flows from the reference source M, to the seconddigital source P through the resistance R the Z-diode D and the thirdvoltage divider R R By virtue of the voltage drop across the resistanceR the base of the first transistor Tr, is more positive than itsemitter, so that the transistor Tr, becomes conductive and, as alreadyset forth hereinabove, it transmits an 0 potential to the output 1. Thecurrent flowing from the reference source M, to the second digitalsource P effects such a voltage drop across the third voltage divider RR that its center tap and thus also the base of thetransistor Tr willhave a negative potential, so that the transistor Tr will becomeconductive. As a result, at the output 2 again an 0 potential appears.

In view of the foregoing, the following table may be set up for thedetector shown in FIG. 3:

State of Potential at Input E Output 1 Output 2 Negative Potential 1 0Ground Potential 0 l Floating Ground and Floating Potential 0 0 Theresistance R determines the input resistance of the detector withrespect to the negative potential, while the Z-diode D and the thirdvoltage divider R R determines the input resistance with respect to theground. If the input resistance is to be of a high ohmic value, then R Rand R all have a large resistance. Further, the Z-diode D determines theswitching threshold in which the detector recognizes the groundpotential. For reasons set forth in the introduction, its blockingvoltage in the present case 1 potential equals 5 V) should be at least 5V, since the higher the blocking voltage, the greater is the voltagerange in which the scanning device reports a ground potential". Itsupper value is determined by the requirement that between the tworesistances R and R of the third voltage divider, there should remain anegative potential to permit the control of the transistor Tr The rangein which the detector reports a negative potential may be set by meansof an external adjustment effected at M,. Normally, the detector reportsa negative potential" only when at the input E there prevails apotential which is either equal to or more negative than that at M,. Byraising or lowering the negative potential at M, by voltage dividercircuits, the switching threshold for the negative potential may beraised or lowered to the same extent.

What is claimed is:

1. A detector for sensing and digitally encoding a plurality of statesof potentials applied to a signal input thereof comprising, incombination:

a. a plurality of semiconductor components, each component having first,second and third terminal means, and a signal input terminal means, eachof said signal input terminal means being coupled to i said signal inputfor applying the states of potential to be encoded to each saidsemiconductor component;

a plurality of digital signal sources delivering digital l and digitalpotentials, each of said first terminal. means being coupledrespectively to a respective one of said digital sources;

c. a plurality of reference sources delivering potentials smaller thanthe 0 potential and greater than the 1 potential, each said secondterminal means being coupled respectively to a respective one of saidreference sources;

. a plurality of comparison sources delivering potentials with which thestates of potential applied to said signal input are compared, each saidthird terminal means being coupled respectively to a respective one ofsaid comparison sources for placing selectively each said semiconductorcom ponent into a conductive and blocking state in response to thedifference of potential between the particular state of potential beingapplied to said signal input and the potential supplied from respectiveones of said comparison sources;

e. a plurality of voltage dividers, each voltage divider beingpositioned in a respective current path which includes a respective saidfirst terminal means and a respective said third terminal means and eachvoltage dividerhaving a tap; and

f. a plurality of output terminals, each output terminal being coupledto a respective one of said taps.

2. A detector as defined in claim 1, wherein said semiconductorcomponents are two in number and comprise respectively a first and asecond transistor and wherein said reference source associated with saidfirst transistor comprises said comparison sources for both transistors.

3. A detector as defined in claim 2, wherein the potential of saidreference sources corresponds to thelowest one of said states ofpotential and all said digital sources deliver a 1 potential.

4. A detector as defined in claim 3, wherein said first transistor is ann-p-n transistor and said second transistor is a p-n-p transistor; andsaid detector includes:

a resistance of high ohmic value having a first end connected to saidsignal input and to the base of said first transistor and a second endconnected to the emitter of said first transistor and to the referencesource associated therewith,

a Zener diode connected to said signal input, and

an additional voltage divider having one end connected to said Zenerdiode and another end connected to the digital source associated withsaid second transistor and to the emitter of said second transistor; andwherein said additional voltage divider is formed of two resistancescoupled to a center tap which is connected to the base of said secondtransistor and the ratio of resistances in said additional voltagedivider is such that in the conductive state of said Zener diode, thebase of said second transistor is negative with respect to the emitterthereof.

5. A detector as defined in claim 4, wherein the digital sourceassociated with said second transistor has a 1 potential and said Zenerdiode has a gating voltage corresponding to the desired switchingthreshold for the highest state of potential, said gating voltage beingat least identical to the 1 potential.

6. A detector as defined in claim 5, wherein the voltage dividerassociated with said first transistor is connected at one end to thecollector of said first transistor and at the other end to the digitalsource associated with said first transistor; one resistance of thevoltage divider associated with said second transistor is connected tothe digital source associated with said second transistor and to theemitter thereof; and the other resistance of the last-named voltagedivider is connected to the collector of the second transistor and tothe reference source associated therewith.

7. A detector as defined in claim 2, further comprising a first diodeand a second diode;'and wherein the taps of said voltage dividersassociated with said first and said second transistors are connected toa zero reference potential point through the respective said first andsaid second diodes. I

1. A detector for sensing and digitally encoding a plurality of statesof potentials applied to a signal input thereof comprising, incombination: a. a plurality of semiconductor components, each componenthaving first, second and third terminal means, and a signal inputterminal means, each of said signal input terminal means being coupledto said signal input for applying the states of potential to be encodedto each said semiconductor component; b. a plurality of digital signalsources delivering digital 1 and digital 0 potentials, each of saidfirst terminal means being coupled respectively to a respective one ofsaid digital sources; c. a plurality of reference sources deliveringpotentials smaller than the 0 potential and greater than the 1potential, each said second terminal means being coupled respectively toa respective one of said reference sources; d. a plurality of comparisonsources delivering potentials with which the states of potential appliedto said signal input are compared, each said third terminal means beingcoupled respectively to a respective one of said comparison sources forplacing selectively each said semiconductor component into a conductiveand blocking state in response to the difference of potential betweenthe particular state of potential being applied to said signal input andthe potential supplied from respective ones of said comparison sources;e. a plurality of voltage dividers, each voltage divider beingpositioned in a respective current path which includes a respective saidfirst terminal means and a respective said third terminal means and eachvoltage divider having a tap; and f. a plurality of output terminals,each output terminal being coupled to a respective one of said taps. 2.A detector as defined in claim 1, wherein said semiconductor componentsare two in number and comprise respectively a first and a secondtransistor and wherein said reference source associated with said firsttransistor comprises said comparison sources for both transistors.
 3. Adetector as defined in claim 2, wherein the potential of said referencesources corresponds to the lowest one of said states of potential andall said digital sources deliver a 1 potential.
 4. A detector as definedin claim 3, wherein said first transistor is an n-p-n transistor andsaid second transistor is a p-n-p transistor; and said detectorincludes: a resistance of high ohmic value having a first end connectedto said signal input and to the base of said first transistor and asecond end connected to the emitter of said first transistor and to thereference source associated therewith, a Zener diode connected to saidsignal input, and an additional voltage divider having one end connectedto said Zener diode and another end connected to the digital sourceassociated with said second transistor and to the emitter of said secondtransistor; and wherein said additional voltage divider is formed of tworesistances coupled to a center tap which is connected to the base ofsaid second transistor and the ratio of resistances in said additionalvoltage divider is such that in the conductive state of said Zenerdiode, the base of said second transistor is negative with respect tothe emitter thereof.
 5. A detector as defined in claim 4, wherein thedigital source associated with said second transistor has a 1 potentialand said Zener diode has a gating voltage corresponding to the desiredswitching threshold for the highest state of potential, said gatingvoltage being at least identical to the 1 potential.
 6. A detector asdefined in claim 5, wherein the voltage divider associated with saidfirst transistor is connected at one end to the collector of said firsttransistor and at the other end to the digital source associated withsaid first transistor; one resistance of the voltage divider associatedwith said second transistor is connected to the digital sourceassociated with said second transistor and to the emitter thereof; andthe other resistance of the last-named voltage divider is connected tothe collector of the second transistor and to the reference sourceassociated therewith.
 7. A detector as defined in claim 2, furthercomprising a first diode and a second diode; and wherein the taps ofsaid voltage dividers associated with said first and said secondtransistors are connected to a zero reference potential point throughthe respective said first and said second diodes.